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To achieve preferential effects against cancer cells but less damage to normal cells is one of the main challenges of cancer research. In this review, we explore the roles and relationships of oxidative stress-mediated apoptosis, DNA damage, ER stress, autophagy, metabolism, and migration of ROS-modulating anticancer drugs. Understanding preferential anticancer effects in more detail will improve chemotherapeutic approaches that are based on ROS-modulating drugs in cancer treatments., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The natural compound sinularin, isolated from marine soft corals, is antiproliferative against several cancers, but its possible selective killing effect has rarely been investigated. This study investigates the selective killing potential and mechanisms of sinularin-treated breast cancer cells. In 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H- tetrazolium, inner salt (MTS) assay, sinularin dose-responsively decreased the cell viability of two breast cancer (SKBR3 and MDA-MB-231) cells, but showed less effect on breast normal (M10) cells after a 24 h treatment. According to 7-aminoactinomycin D (7AAD) flow cytometry, sinularin dose-responsively induced the G2/M cycle arrest of SKBR3 cells. Sinularin dose-responsively induced apoptosis on SKBR3 cells in terms of a flow cytometry-based annexin V/7AAD assay and pancaspase activity, as well as Western blotting for cleaved forms of poly(ADP-ribose) polymerase (PARP), caspases 3, 8, and 9. These caspases and PARP activations were suppressed by N -acetylcysteine (NAC) pretreatment. Moreover, sinularin dose-responsively induced oxidative stress and DNA damage according to flow cytometry analyses of reactive oxygen species (ROS), mitochondrial membrane potential (MitoMP), mitochondrial superoxide, and 8-oxo-2'-deoxyguanosine (8-oxodG)). In conclusion, sinularin induces selective killing, G2/M arrest, apoptosis, and oxidative DNA damage of breast cancer cells., Competing Interests: The authors declare no conflict of interest.

Reactive oxygen species (ROS) induction had been previously reported in 4β-hydroxywithanolide (4βHWE)-induced selective killing of oral cancer cells, but the mechanism involving ROS and the DNA damage effect remain unclear. This study explores the role of ROS and oxidative DNA damage of 4βHWE in the selective killing of oral cancer cells. Changes in cell viability, morphology, ROS, DNA double strand break (DSB) signaling (γH2AX foci in immunofluorescence and DSB signaling in western blotting), and oxidative DNA damage (8-oxo-2'deoxyguanosine [8-oxodG]) were detected in 4βHWE-treated oral cancer (Ca9-22) and/or normal (HGF-1) cells. 4βHWE decreased cell viability, changed cell morphology and induced ROS generation in oral cancer cells rather than oral normal cells, which were recovered by a free radical scavenger N-acetylcysteine (NAC). For immunofluorescence, 4βHWE also accumulated more of the DSB marker, γH2AX foci, in oral cancer cells than in oral normal cells. For western blotting, DSB signaling proteins such as γH2AX and MRN complex (MRE11, RAD50, and NBS1) were overexpressed in 4βHWE-treated oral cancer cells in different concentrations and treatment time. In the formamidopyrimidine-DNA glycolyase (Fpg)-based comet assay and 8-oxodG-based flow cytometry, the 8-oxodG expressions were higher in 4βHWE-treated oral cancer cells than in oral normal cells. All the 4βHWE-induced DSB and oxidative DNA damage to oral cancer cells were recovered by NAC pretreatment. Taken together, the 4βHWE selectively induced DSB and oxidative DNA damage for the ROS-mediated selective killing of oral cancer cells., (© 2017 Wiley Periodicals, Inc.)

Purpose Radiation combined with natural products may improve the radiosensitivity of cancer cells. This study investigated the potential of a combined modality treatment with Ultraviolet C (UVC; wavelength range 200-280 nm) and our previously identified anti-oral cancer agent (methanolic extracts of Cryptocarya concinna roots; MECCrt) in oral cancer cells. Materials and methods The mechanism of the possible synergy of UVC and MECCrt was explored in terms of cell viability, cell cycle, apoptosis, reactive oxygen species (ROS), mitochondrial membrane potential (MitoMP), and DNA damage analyses. Results In cell viability (%) at 24 h treatment, the low doses of UVC (14 J/m(2)) and MECCrt (10 μg/ml) resulted in slight damage to human oral cancer Ca9-22 cells (83.2 and 80.4) but was less harmful to human oral normal HGF-1 cells (93.4 and 91.8, respectively). The combined treatment of UVC and MECCrt (UVC/MECCrt) had a lower viability (54.5%) than UVC or MECCrt alone in Ca9-22 cells but no showed significant change in HGF-1 cells. In Ca9-22 cells, the expression of flow cytometry-based apoptosis (sub-G1 phase, annexin V, and pancaspase assays) was significantly higher in UVC/MECCrt than in UVC or MECCrt alone (p < 0.0001). Using flow cytometry, intracellular ROS levels of UVC/MECCrt and MECCrt alone were higher than for UVC alone. MitoMP change and H2A histone family member X (γH2AX; H2AFX)-based DNA damage were synergistically inhibited and induced by MECCrt/UVC compared to its single treatment in Ca9-22 cells, respectively. Conclusion UVC plus MECCrt treatment had selective killing and synergistic anti-proliferative effects against oral cancer cells involving apoptosis, oxidative stress, and DNA damage. This combination therapy appears to have a great clinical potential against oral cancer cells.

Background: Grape seeds extract (GSE) is a famous health food supplement for its antioxidant property. Different concentrations of GSE may have different impacts on cellular oxidative/reduction homeostasis. Antiproliferative effect of GSE has been reported in many cancers but rarely in oral cancer., Methods: The aim of this study is to examine the antioral cancer effects of different concentrations of GSE in terms of cell viability, apoptosis, reactive oxygen species (ROS), mitochondrial function, and DNA damage., Results: High concentrations (50-400 μg/ml) of GSE dose-responsively inhibited proliferation of oral cancer Ca9-22 cells but low concentrations (1-10 μg/ml) of GSE showed a mild effect in a MTS assay. For apoptosis analyses, subG1 population and annexin V intensity in high concentrations of GSE-treated Ca9-22 cells was increased but less so at low concentrations. ROS generation and mitochondrial depolarization increased dose-responsively at high concentrations but showed minor changes at low concentrations of GSE in Ca9-22 cells. Additionally, high concentrations of GSE dose-responsively induced more γH2AX-based DNA damage than low concentrations., Conclusions: Differential concentrations of GSE may have a differentially antiproliferative function against oral cancer cells via differential apoptosis, oxidative stress and DNA damage.

Radiotherapy effectively destroys cancer cells in many sites of the body, but several limitations remain. This study investigated alternative splicing, which is a common mechanism of increased diversity in mRNAs and proteins. The relationships of alternative splicing to DNA damage and radiation such as UV and ionizing radiation were analyzed. The DNA damage responses of many genes involved in alternative splicing were compared between non-radiation and radiation treatments. Drugs that affect radioresistence or radiosensitization by modulating the effects of alternative splicing and radiation were also reviewed.

Data obtained through high-throughput technologies have gradually revealed that a unique stratified epithelial architecture of human skin along with the antioxidant-response pathways provided vital defensive mechanisms against UV radiation. However, it is noteworthy that skin is a major target for toxic insult by UV radiations that can alter its structure and function. Substantial fraction of information has been added into the existing pool of knowledge related to natural products mediated biological effects in UV exposed skin cells. Accumulating evidence has started to shed light on the potential of these bioactive ingredients as protective natural products in cosmetics against UV photodamage by exerting biological effects mainly through wide ranging intracellular signalling cascades of oxidative stress and modulation of miRNAs. In this review, we have summarized recently emerging scientific evidences addressing underlying mechanisms of UV induced oxidative stress and deregulation of signalling cascades and how natural products can be used tactfully to protect against UV induced harmful effects.

Background: Most chemotherapeutic drugs for killing cancer cells are highly cytotoxic in normal cells, which limits their clinical applications. Therefore, a continuing challenge is identifying a drug that is hypersensitive to cancer cells but has minimal deleterious effects on healthy cells. The aims of this study were to evaluate the potential of 4β-hydroxywithanolide (4βHWE) for selectively killing cancer cells and to elucidate its related mechanisms., Methodology and Principal Findings: Changes in survival, oxidative stress, DNA damage, and apoptosis signaling were compared between 4βHWE-treated oral cancer (Ca9-22) and normal fibroblast (HGF-1) cells. At 24 h and 48 h, the numbers of Ca9-22 cells were substantially decreased, but the numbers of HGF-1 cells were only slightly decreased. Additionally, the IC50 values for 4βHWE in the Ca9-22 cells were 3.6 and 1.9 µg/ml at 24 and 48 h, respectively. Time-dependent abnormal increases in ROS and dose-responsive mitochondrial depolarization can be exploited by using 4βHWE in chemotherapies for selectively killing cancer cells. Dose-dependent DNA damage measured by comet-nuclear extract assay and flow cytometry-based γ-H2AX/propidium iodide (PI) analysis showed relatively severer damage in the Ca9-22 cells. At both low and high concentrations, 4βHWE preferably perturbed the cell cycle in Ca9-22 cells by increasing the subG1 population and arrest of G1 or G2/M. Selective induction of apoptosis in Ca9-22 cells was further confirmed by Annexin V/PI assay, by preferential expression of phosphorylated ataxia-telangiectasia- and Rad3-related protein (p-ATR), and by cleavage of caspase 9, caspase 3, and poly ADP-ribose polymerase (PARP)., Conclusions/significance: Together, the findings of this study, particularly the improved understanding of the selective killing mechanisms of 4βHWE, can be used to improve efficiency in killing oral cancer cells during chemoprevention and therapy.

Background: Methanolic extracts of Gracilaria tenuistipitata (MEGT) were obtained from the edible red algae. Previously, we found that water extract of G. tenuistipitata was able to modulate oxidative stress-induced DNA damage and its related cellular responses., Methods: In this study, the methanol extraction product MEGT was used to evaluate the cell growth inhibition in oral cancer cells and its possible mechanism was investigated., Results: The cell viability of MEGT treated Ca9-22 oral cancer cell line was significantly decreased in a dose-response manner (p < 0.05). The sub-G1 population and annexin V intensity of MEGT-treated Ca9-22 cancer cells were significantly increased in a dose-response manner (p < 0.0005 and p < 0.001, respectively). The γH2AX intensities of MEGT-treated Ca9-22 cancer cells were significantly increased in a dose-response manner (p < 0.05). The reactive oxygen species (ROS) and glutathione (GSH)-positive intensities of MEGT-treated Ca9-22 oral cancer cells were significantly increased and decreased, respectively, in a dose-response manner (p < 0.05). The DiOC2(3) intensity for mitochondrial membrane potential (MMP) of MEGT-treated Ca9-22 cancer cells was significantly decreased in a dose-response manner (p < 0.05)., Conclusions: These results indicated that MEGT had apoptosis-based cytotoxicity against oral cancer cells through the DNA damage, ROS induction, and mitochondrial depolarization. Therefore, MEGT derived from the edible algae may have potential therapeutic effects against oral squamous cell carcinoma (OSCC).

Potential antioxidant properties of an aqueous extract of the edible red seaweed Gracilaria tenuistipitata (AEGT) against oxidative DNA damage were evaluated. The AEGT revealed several antioxidant molecules, including phenolics, flavonoids and ascorbic acid. In a cell-free assay, the extract exhibited 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity that significantly reduced H₂O₂-induced plasmid DNA breaks in a dose-response manner (P < 0.001). The AEGT also suppressed H₂O₂-induced oxidative DNA damage in H1299 cells by reducing the percentage of damaged DNA in a dose-response manner (P < 0.001) as measured by a modified alkaline comet-nuclear extract (comet-NE) assay. The MTT assay results showed that AEGT confers significant protection against H₂O₂-induced cytotoxicity and that AEGT itself is not cytotoxic (P < 0.001). Moreover, H₂O₂-induced cell cycle G2/M arrest was significantly released when cells were co-treated with different concentrations of AEGT (P < 0.001). Taken together, these findings suggest that edible red algae Gracilaria water extract can prevent H₂O₂-induced oxidative DNA damage and its related cellular responses.

The antibiotic antimycin A (AMA) is commonly used as an inhibitor for the electron transport chain but its application in anticancer studies is rare. Recently, the repurposing use of AMA in antiproliferation of several cancer cell types has been reported. However, it is rarely investigated in oral cancer cells. The purpose of this study is to investigate the selective antiproliferation ability of AMA treatment on oral cancer cells. Cell viability, flow cytometry, and western blotting were applied to explore its possible anticancer mechanism in terms of both concentration‐ and exposure time‐effects. AMA shows the higher antiproliferation to two oral cancer CAL 27 and Ca9‐22 cell lines than normal oral HGF‐1 cell lines. Moreover, AMA induces the production of higher reactive oxygen species (ROS) levels and pan‐caspase activation in oral cancer CAL 27 and Ca9‐22 cells than in normal oral HGF‐1 cells, providing the possible mechanism for its selective antiproliferation effect of AMA. In addition to ROS, AMA induces mitochondrial superoxide (MitoSOX) generation and depletes mitochondrial membrane potential (MitoMP). This further supports the AMA‐induced oxidative stress changes in oral cancer CAL 27 and Ca9‐22 cells. AMA also shows high expressions of annexin V in CAL 27 and Ca9‐22 cells and cleaved forms of poly (ADP‐ribose) polymerase (PARP), caspase 9, and caspase 3 in CAL 27 cells, supporting the apoptosis‐inducing ability of AMA. Furthermore, AMA induces DNA damage (γH2AX and 8‐oxo‐2′‐deoxyguanosine [8‐oxodG]) in CAL 27 and Ca9‐22 cells. Notably, the AMA‐induced selective antiproliferation, oxidative stress, and DNA damage were partly prevented from N‐acetylcysteine (NAC) pretreatments. Taken together, AMA selectively kills oral cancer cells in an oxidative stress‐dependent mechanism involving apoptosis and DNA damage. [ABSTRACT FROM AUTHOR]

LY303511 was developed as a negative control of LY294002 without pan‐phosphoinositide 3‐kinase (PI3K) inhibition. We hypothesize LY303511 generate reactive oxygen species (ROS) to induce apoptosis for killing oral cancer cells. In MTS assay, LY303511 dose‐responsively decreases survival in three kinds of oral cancer cells but little damage to normal oral cells (HGF‐1). Two oral cancer cells (CAL 27 and SCC‐9) with highly sensitivity to LY303511 were used. In 7‐aminoactinomycin D (7AAD) assay, LY303511 slightly increases subG1 population in oral cancer cells. In annexin V/7AAD and/or pancaspase assays, LY303511 induces apoptosis in oral cancer cells but HGF‐1 cells remains in basal level. In oxidative stress, LY303511 induces ROS and mitochondrial superoxide in oral cancer cells. In 8‐oxo‐2'‐deoxyguanosine assay, LY303511 induces oxidative DNA damage in oral cancer cells. In zebrafish model, LY303511 inhibits CAL 27‐xenografted tumor growth. Therefore, LY303511 displays antiproliferation potential against oral cancer cells in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Simple Summary: Combined treatments with low side effects enhance anticancer applications. This study focusses on validating the potential synergistic antiproliferation of the combined treatment of ultraviolet-C and the coral-derived compound sinularin (UVC/sinularin) in oral cancer cells. This study confirms that UVC/sinularin synergistically and selectively inhibits oral cancer cell proliferation with low cytotoxicity on normal oral cells. The mechanisms involve the enhanced cellular and mitochondrial oxidative stress that cause apoptosis, DNA damage, and mitochondrial dysfunction in oral cancer cells. Combined treatment is increasingly used to improve cancer therapy. Non-ionizing radiation ultraviolet-C (UVC) and sinularin, a coral Sinularia flexibilis-derived cembranolide, were separately reported to provide an antiproliferation function to some kinds of cancer cells. However, an antiproliferation function using the combined treatment of UVC/sinularin has not been investigated as yet. This study aimed to examine the combined antiproliferation function and explore the combination of UVC/sinularin in oral cancer cells compared to normal oral cells. Regarding cell viability, UVC/sinularin displays the synergistic and selective killing of two oral cancer cell lines, but remains non-effective for normal oral cell lines compared to treatments in terms of MTS and ATP assays. In tests using the flow cytometry, luminescence, and Western blotting methods, UVC/sinularin-treated oral cancer cells exhibited higher reactive oxygen species production, mitochondrial superoxide generation, mitochondrial membrane potential destruction, annexin V, pan-caspase, caspase 3/7, and cleaved-poly (ADP-ribose) polymerase expressions than that in normal oral cells. Accordingly, oxidative stress and apoptosis are highly induced in a combined UVC/sinularin treatment. Moreover, UVC/sinularin treatment provides higher G2/M arrest and γH2AX/8-hydroxyl-2′deoxyguanosine-detected DNA damages in oral cancer cells than in the separate treatments. A pretreatment can revert all of these changes of UVC/sinularin treatment with the antioxidant N-acetylcysteine. Taken together, UVC/sinularin acting upon oral cancer cells exhibits a synergistic and selective antiproliferation ability involving oxidative stress-dependent apoptosis and cellular DNA damage with low toxic side effects on normal oral cells. [ABSTRACT FROM AUTHOR]

Some lichens provide the resources of common traditional medicines and show anticancer effects. However, the anticancer effect of Usnproliea barbata (U. barbata) is rarely investigated, especially for oral cancer cells. The aim of this study was to investigate the cell killing function of methanol extracts of U. barbata (MEUB) against oral cancer cells. MEUB shows preferential killing against a number of oral cancer cell lines (Ca9-22, OECM-1, CAL 27, HSC3, and SCC9) but rarely affects normal oral cell lines (HGF-1). Ca9-22 and OECM-1 cells display the highest sensitivity to MEUB and were chosen for concentration effect and time course experiments to address its cytotoxic mechanisms. MEUB induces apoptosis of oral cancer cells in terms of the findings from flow cytometric assays and Western blotting, such as subG1 accumulation, annexin V detection, and pancaspase activation as well as poly (ADP-ribose) polymerase (PARP) cleavage. MEUB induces oxidative stress and DNA damage of oral cancer cells following flow cytometric assays, such as reactive oxygen species (ROS)/mitochondrial superoxide (MitoSOX) production, mitochondrial membrane potential (MMP) depletion as well as overexpression of γH2AX and 8-oxo-2′deoxyguanosine (8-oxodG). All MEUB-induced changes in oral cancer cells were triggered by oxidative stress which was validated by pretreatment with antioxidant N-acetylcysteine (NAC). In conclusion, MEUB causes preferential killing of oral cancer cells and is associated with oxidative stress, apoptosis, and DNA damage. [ABSTRACT FROM AUTHOR]